The education secretary also refused to be drawn on how many of the selective schools would be created, stating it would be decided locally.
Her appearance on ITV’s Peston on Sunday comes just days after prime minister Theresa May vowed to establish the first grammar school in 50 years at the Conservative Party conference in Birmingham on Wednesday.
Speaking this morning, Ms Greening repeated the government’s claims that there would be no return to the “binary system” of grammar schools and secondary moderns in the 1950s.
“This is absolutely not about a return to the 11-plus, and one of the areas we are consulting on is whether children should be able to go into selective schools at different ages, rather than just at age 11,” the Cabinet member said on ITV’s Peston on Sunday.
“We have to understand that children develop at different paces and our education system needs to reflect that.”
Asked whether she wanted to see a doubling of grammar schools, Ms Greening said any decision about the number of grammars would be decided at a local level.
“In terms of the numbers, that is going to be up to the local communities,” she said.
“I want to see parents have more choice. We think it’s wrong that in this particular part of the education system, while there is so much more additional choice come into play in recent years, grammars have been put to one side.
“We want a 21st Century education system but that means we have to look at the role grammars can play,” Ms Greening added.
The education secretary also hinted that the changes would see greater emphasis being placed on grammar schools to take on more children from disadvantaged backgrounds and to do more for non-selective schools in their area.
Responding on the show, Alistair Campbell, Tony Blair’s former director of communications, said Ms Greening was “womanfully defending” policies she didn’t believe in.
Ms Greening also said she would “look carefully” on how the government can make sex and relationships education “fit for the world children are growing up in” today.